Novel Polymorphs of Efavirenz

ABSTRACT

The present invention relates to novel amorphous and crystalline forms of efavirenz, processes for their preparation and pharmaceutical compositions containing them. In accordance with the present invention efavirenz crude is dissolved in acetone at 25° C.-30° C., the solution is slowly added to water for 30 minutes at 0° C.-5° C., stirred for 1 hour at the same temperature, the separated solid is filtered, washed with water and dried at 55° C.-60° C. for 5 hours to give amorphous efavirenz.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 13/174,893filed on July 1, 2011, which is a continuation of U.S. patentapplication Ser. No. 10/568,904, filed on Feb. 17, 2006, which is a 371of PCT/IN2004/000250, filed on Aug. 19, 2004, which is incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to novel polymorphs of efavirenz,processes for their preparation and pharmaceutical compositionscontaining them.

BACKGROUND OF THE INVENTION

The present invention relates to novel polymorphs of efavirenz,processes for their preparation and pharmaceutical compositionscontaining them.

Pharmaceutical products with HIV reverse transcriptase (including itsresistant varieties) inhibitors are described in U.S. Pat. No.5,519,021. An especially important compound among those disclosed isefavirenz,(4S)-6-chloro-4-(cyclopropylethynyl)-1,4-dihydro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one.Efavirenz has the following structural formula:

This compound is used for the preparation of a medicament havingnonnucleoside HIV-1 reverse transcriptase inhibiting activity that isuseful in the prevention or treatment of infection by HIV and thetreatment of AIDS. Efavirenz is sold commercially as SUSTIVA® by BristolMyers Squibb.

WO patent application publication No. 98/33782 disclosed threecrystalline forms, Form I (characterized by an x-ray powder diffractionpatterns having peaks expressed as 2θ at 6.1, 6.4, 10.4, 10.9, 12.3,13.2, 14.2, 15.2, 16.9, 18.4, 19.2, 20.1, 21.2, 22.3, 23.0, 24.9, 25.9,26.3, 27.2, 28.1, 28.6, 29.1, 29.5, 30.7, 32.4 and 38.3 degrees), FormII (characterized by an x-ray powder diffraction patterns having peaksexpressed as 2θ at 3.6, 6.3, 11.1, 12.8, 13.3, 14.3, 16.1, 16.9, 18.5,19.2, 19.6, 20.6, 21.3, 22.6, 23.2, 24.4, 24.9, 26.0, 26.8, 27.6, 28.4,29.2, 29.6, 30.6, 31.9 and 33.8 degrees) and Form III (characterized byan x-ray powder diffraction patterns having peaks expressed as 2θ at7.2, 10.9, 13.7, 14.5, 16.7, 19.1, 19.6, 20.8, 21.7, 22.3, 22.8, 23.2,23.9, 24.5, 24.9, 25.8, 27.0, 27.6, 29.3, 30.3, 30.7, 31.3, 33.4, 38.4and 39.2 degrees) of efavirenz.

WO patent application publication No. 99/64405 disclosed fivecrystalline forms, Form 1(characterized by an x-ray powder diffractionpatterns having peaks expressed as 2θ at about 6.0, 6.3, 10.3, 10.8,14.1, 16.8, 20.0, 20.5, 21.1 and 24.8 degrees), Form 2 (characterized byan x-ray powder diffraction patterns having peaks expressed as 2θ atabout 6.8, 9.2, 12.3, 16.2, 21.4, 22.7, 24.1 and 28.0 degrees), Form 3(characterized by an x-ray powder diffraction patterns having peaksexpressed as 2θ at about 7.1, 7.3, 11.0, 13.8, 20.9, 23.3, 27.9 and 33.5degrees), Form 4 (characterized by an x-ray powder diffraction patternshaving peaks expressed as 2θ at about 3.6, 6.3, 9.7, 11.0, 12.7, 13.2,16.1, 19.2, 19.5, 20.6 and 24.3 degrees) and Form 5 (characterized by anx-ray powder diffraction patterns having peaks expressed as 2θ at about10.2, 11.4, 11.6, 12.6, 19.1, 20.6, 21.3, 22.8, 24.8, 27.4, 28.2 and31.6 degrees) of efavirenz.

We have discovered a stable novel crystalline form of efavirenz. Thenovel form is at least as stable as the reported forms (Form I, Form II,Form III, Form 1, Form 2, Form 3, Form 4 and Form 5). The novelcrystalline form is stable over the time and has good flow propertiesand so, the novel crystalline form is suitable for formulatingefavirenz.

Amorphous form of efavirenz has not been reported in the prior art. So,there is a need for stable amorphous form of efavirenz for betterpharmaceutical preparations.

One object of the present invention is to provide a stable novelcrystalline form of efavirenz, process for preparing it and apharmaceutical composition containing it.

Another object of the present invention is to provide a novel stableamorphous form of efavirenz, process for preparing it and apharmaceutical composition containing it.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, there is provided a novelamorphous form of efavirenz. The amorphous efavirenz is characterized byhaving broad x-ray diffraction spectrum as in FIG. 1.

In accordance with the present invention, a process is provided forpreparation of amorphous efavirenz, which comprises:

precipitating from a solution of efavirenz in a C₃-C₈-ketonic solvent byusing water as precipitating solvent at below about 15° C., andcollecting the precipitated solid; and

drying the solid collected at about 40° C.-65° C. to obtain amorphousefavirenz.

The preferable ketonic solvent is selected from acetone, methyl ethylketone, methyl isobutyl ketone, methyl tert-butyl ketone and diethylketone; more preferable ketonic solvent is selected from acetone anddiethyl ketone; and still more preferable ketonic solvent is acetone.

The solution of efavirenz in the ketonic solvent may be prepared bydissolving efavirenz in a known form or in crystalline form H1 describedbelow in the said ketonic solvent. Alternatively, crude efavirenz mayalso be used in the process.

Preferably the precipitation is carried out at about 0° C.-10° C. andmore preferably at about 2° C.-5° C.

The precipitated solid may be collected by filtration or centrifugation.

The preferable temperature range of drying is at about 50° C.-60° C. andmore preferable temperature range is at about 55° C.-60° C.

Preferably the process is carried out by precipitating from a solutionof efavirenz in a C₃-C₈-ketonic solvent, preferably acetone, by addingthe said solution to water at about 0° C.-10° C. and more preferably atabout 2° C.-5° C.; collecting the precipitated solid by filtration orcentrifugation; and drying the solid collected at about 40° C.-65° C.,more preferably at about 55° C.-60° C. to obtain amorphous efavirenz.

The novel amorphous efavirenz is found to have better dissolutionproperties when compared with the known forms.

In accordance with the present invention, there is provided a novelcrystalline form of efavirenz, designated as form H1, characterized byan x-ray powder diffraction spectrum having peaks expressed as 2θ atabout 5.4, 10.4, 11.6, 12.5, 15.3, 20.1, 20.8, 22.5, 23.1, 25.7, 27.9,28.5, 28.8, 29.5, 30.2 and 38.2 degrees. FIG. 2 shows typical form H1x-ray powder diffraction spectrum.

In accordance with the present invention, a process is provided forpreparation of efavirenz form H1, which comprises:

-   a) precipitating from a solution of efavirenz in a C₁-C₆-alcoholic,    C₃-C₈-ketonic solvent or a mixture thereof by using water as    precipitating solvent at below about 15° C., collecting the    precipitated solid;-   b) drying the solid collected at about 25° C.-35° C. until the water    content falls in the range 2-10% of the solid by weight; and-   c) drying the solid obtained in (b) at about 40° C.-55° C. to obtain    crystalline efavirenz form H1.

The preferable alcoholic solvent is selected from ethanol, n-propanol,n-butanol, isopropanol and methanol and more preferable alcoholicsolvent is n-propanol.

The preferable ketonic solvent is selected from acetone, methyl ethylketone, methyl isobutyl ketone, methyl tert-butyl ketone and diethylketone; more preferable ketonic solvent is selected from acetone anddiethyl ketone; and still more preferable ketonic solvent is acetone.

The solution of efavirenz in the ketonic or alcoholic solvent may beprepared by dissolving efavirenz in a known form or in amorphous form inthe said ketonic or alcoholic solvent. Alternatively, crude efavirenzmay also be used in the process.

Preferably the precipitation is carried out at about 0° C.-10° C. andmore preferably at about 2° C.-5° C.

The precipitated solid may be collected by filtration or centrifugation.

It has been found that the drying of precipitated product in step (a)directly at higher temperature leads to known crystalline form 1 (WOpatent application publication No. 99/64405).

Preferably the drying in step (b) is carried out until the water contentfalls in the range 2-5% of the solid by weight.

The preferable temperature range of drying in step (c) is at about 40°C.-50° C. and more preferably at about 40° C.-45° C.

Preferably the process is carried out by precipitating from a solutionof efavirenz in a C₁-C₆-alcoholic solvent, preferably n-propanol orisopropanol, C₃-C₈-ketonic solvent, preferaly acetone or diethyl ketone,or a mixture thereof by adding the said solution to water at about 0°C.-10° C. and more preferably at about 2° C.-5° C.; collecting theprecipitated solid by filtration or centrifugation; drying theprecipitated solid at about 25° C.-35° C. until the water content is2-5%; and drying the solid obtained at about 40° C.-55° C., preferablyat about 40° C.-50° C., to obtain crystalline efavirenz form H1.

Unless otherwise specified, the alkyl portion of the C₁ to C₅-alcoholand C₃ to C₈-ketone used can be straight or branch, unsubstituted orsubstituted with for example alkoxy, halogen, nitro, cyano or hydroxygroups.

The novel crystalline efavirenz form H1 is at least as stable as thereported forms (Form I, Form II, Form III, Form 1, Form 2, Form 3, Form4 and Form 5). The novel crystalline form is stable over the time andhas good flow properties and so, the novel crystalline form is suitablefor formulating efavirenz.

The above novel polymorphs of efavirenz are useful for the preparationof medicaments having nucleoside HIV-1 reverse transcriptase inhibitingactivity that is useful in the prevention or treatment of infection byHIV and the treatment of aids. The novel polymorphs of efavirenz can beused in pharmaceutical compositions generally in combination with atleast one pharmaceutically acceptable excipient.

All the patents mentioned above are incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a x-ray powder diffraction spectrum of amorphous form ofefavirenz.

FIG. 2 is a x-ray powder diffraction spectrum of efavirenz form H1.

x-Ray powder diffraction spectrum was measured on a Bruker axs D8advance x-ray powder diffractometer having a copper-Kα radiation.

The following examples are given for the purpose of illustrating thepresent invention and should not be considered as limitations on thescope or spirit of the invention.

EXAMPLE 1

Efavirenz crude (5 gm, obtained by the process described in example 6,step A to step D, of U.S. Pat. No. 5,519,021) is dissolved in acetone(20 ml) at 25° C.-30° C., slowly added to water (200 ml) for 30 minutesat 0° C.-5° C. and stirred for 1 hour at the same temperature. Then theseparated solid is filtered, washed with water (20 ml) and dried at 55°C.-60° C. for 5 hours to give 4.5 gm of amorphous efavirenz.

EXAMPLE 2

Efavirenz form 1 (10 gm, obtained by the process described in example 8of WO patent application publication No. 99/64405) is dissolved indiethylketone (50 ml) at 25° C.-30° C., slowly added to water (350 ml)for 45 minutes at 0° C.-5° C. and stirred for 2 hours at the sametemperature. Then the separated solid is filtered, washed with water (50ml) and dried at 55° C.-60° C. for 5 hours to give 9.5 gm of amorphousefavirenz.

EXAMPLE 3

Efavirenz crude (5 gm) is dissolved in n-propanol (20 ml) at 25° C.-30°C., slowly added to water (200 ml) for 30 minutes at 0° C.-5° C. andstirred for 1 hour at the same temperature. Then the separated solid isfiltered, washed with water (20 ml) and dried at 25° C.-30° C. for 18hours to obtain efavirenz as wet solid (moisture content: 2.5% by Karlfisher method). The wet solid is dried at 40° C.-45° C. to give 4.4 gmof efavirenz form H1 (water content: 0.3%).

EXAMPLE 4

Amorphous efavirenz (5 gm, obtained in example 1) is dissolved inisopropanol (25 ml) at 25° C.-30° C., slowly added to water (170 ml) for30 minutes at 0° C.-5° C. and stirred for 1 hour 30 minutes at the sametemperature. Then the separated solid is filtered, washed with water (30ml) and dried at 25° C.-30° C. for 20 hours to obtain efavirenz as wetsolid (moisture content: 3.2% by Karl fisher method). The wet solid isdried at 40° C.-45° C. to give 4.3 gm of efavirenz form H1 (watercontent: 0.35%).

1. Amorphous efavirenz.
 2. Amorphous efavirenz according to FIG.
 1. 3. Aprocess for preparation of amorphous efavirenz, which comprising: a)precipitating efavirenz from a solution of efavirenz in a C₃-C₈-ketonicsolvent by adding water as precipitating solvent at a temperature below15° C., and collecting a precipitated solid to provide a collectedsolid; and b) drying the collected solid at a temperature of 40° C.-65°C. to provide amorphous efavirenz.
 4. The process of claim 3, whereinthe C₃-C₈ ketonic solvent is selected from the group consisting ofacetone, methyl ethyl ketone, methyl isobutyl ketone, methyl tert-butylketone, and diethyl ketone.
 5. The process of claim 4, wherein the C₃-C₈ketonic solvent is selected from the group consisting of acetone anddiethyl ketone.
 6. The process of claim 5, wherein the C₃-C₈ ketonicsolvent is acetone.
 7. The process of claim 3, wherein the precipitationin step (a) is carried out at a temperature of 0° C.-10° C.
 8. Theprocess of claim 7, wherein the precipitation is carried out at atemperature of 2° C.-5° C.
 9. The process of claim 3, wherein thetemperature of drying in step b) is 50° C.-60° C.
 10. The process ofclaim 9, wherein the temperature of drying is in step b) 55° C.-60° C.11. The process of claim 3, wherein the process is carried out byprecipitating efavirenz from a solution of efavirenz in a C₃-C₈-ketonicsolvent by adding the solution to water at a temperature of 0° C.-10°C., collecting the precipitated solid by filtration or centrifugationand drying the collected solid at a temperature of 40° C.-65° C. toprovide amorphous efavirenz.
 12. The process of claim 11, wherein theketonic solvent is acetone, the precipitation is carried out at atemperature of 2° C.-5° C. and drying is carried out at a temperature of55° C.-60° C.